This invention relates to access control systems, and in particular to a system and method for utilizing an existing Wiegand infrastructure to support readers and panels with extended data communications functionality.
Access control systems are used for controlling automated access to protected premises, typically through doorways, without requiring in-person security personnel. Typically, a device such as a card reader is positioned near a doorway of a secure area such as a computer room. A person desiring to enter the secure area must present to the reader a card having user data that can be read by the reader. The reader will transmit the user data via a hardwired bus to a control system typically consisting of numerous control panels ultimately connected back to a host computer, which will decide based on certain rules if that person should be allowed to enter the premises at that door. For example, the host computer may be programmed to let certain users in at only certain times of the day, such as normal working hours, or it may be programmed to allow certain users in at all times, or it may be programmed to disallow entry to certain users. If the host computer determines that access should be allowed, it will send a command that will, for example, activate a relay that will open a door strike mechanism, thusly allowing entry by the user that presented the card.
One technology in prevalent use for many years is the wiegand protocol, which utilizes five wires to communicate data and provide power to a dedicated card reader as well known in the art. The five wires are for power, ground, DATA0, DATA1, and LEDCTL. The DATA1 line is a reader output that delivers pulses that are interpreted as binary ones. The DATA0 line is a reader output that delivers pulses that are interpreted as binary zeros. The LEDCTL line is the panel output that determines the state of the LED contained on the reader (off, red, green, or amber). The Wiegand standard protocol well known in the art and is described in detail in “Access Control Standard Protocol for the 26-Bit Wiegand Reader Interface,” by the Security Industry Association. The data bits of the transmission from the reader to the panel typically consists of one or more parity bits and numerous data bits, as described in the aforementioned standard. The definition of the data bits are left to the system designer. For example, one data format uses the first 8 bits as a site code (0–255), and the next 16 bits as the card number (0–65,535).
Certain problems exist with the Wiegand protocol, however. For example, the Wiegand protocol is a one-way protocol, since the reader can send data to the panel but the panel cannot send any data to the reader except to control the door mechanism and a status LED. The ability to detect errors is weak because most Wiegand formats only include a leading and trailing parity bit, and wire runs up to 500 feet in an electrically noisy area enhances the possibility of a data transmission error. Further, if the panel detects a data transmission error, there is no way at the present time for it to signal the error detection back to the reader (to obtain a retransmission). The reader has no method of signaling additional information except the ability to control the reader LED. Moreover, there is no way to attach multiple Wiegand readers in a party-line connection scheme and determine which reader generated the data. Finally, there exists no security (such as encryption) between the reader and the panel.
It is therefore an object of the invention to provide a methodology and system for extending the functionality of the Wiegand protocol such that improved readers and panels may be implemented, without requiring rewiring of the existing Wiegand infrastructure in use today.
It is a further object of the invention to provide such a methodology and system for extending the Wiegand protocol while still allowing prior art Wiegand readers to communicate with the panel, such that existing system can be upgraded with certain readers while still allowing existing readers to function in their original manner.
It is a further object of the invention to provide such a methodology and system for extending the Wiegand protocol that will allow improved functionality in the reader such that the user can provide different types of data inputs to the panel.